Dielectric material



Sept. 29, 1942. A, KEMP 2,296,854

DIELECTRIC MATERIAL.

Filed June 18, 1937 III/I POL YMER/ZED A L/PHA TIC MON0 OL E F INS ANDRUBBER, GUTTA, EAL/1734,01? MINERAL WAX /N l/E N TOR ARKEMP BY A T TORNEV Patented Sept. 29, 1942.

nmuzc'raro Muslim J Archie a. Kemp, Westwoofl, N. 1., assignor to BellTelephone Laboratories, Incorporated. New York, N. Y., a corporation ofNew York Application June 18, 1937, Serial No. 148,878

1 Claim.

This invention relates to electrical insulation and more particularlyfor dielectric materials employed for insulating electrical conductors.

An object of this invention is to insulate electrical apparatuseffectively and eificiently.

A more particular objector this invention is an insulated electricalconductor, .the insulation of which has excellent dielectric properties,is

stable and is free from any corroding materials. Insulation forelectrical apparatus, and ,more

particularly forxdrop wire, in addition topossessing desirableelectrical characteristics, .must withstand the variousconditionstowhich the apparatus is subjected andnot corrode theapparatus. Forexample, a temperature range between 40 F. to +140 F. prevails for dropwire employed extensively as a conductor in telephone communicationsystems and insulation for the drop wire must not flow or crack withouthealing in this temperature range. Then again, the insulation forsubmarine cables. must not be brittle at temperatures which obtain atthe ocean bottom, must not corrode the con-' ductor and most importantof all, must have low leakan'ce and a low dielectric constant.

In accordancejwith this invention, electrical apparatus, and moreparticularly submarine cable, is insulated by a medium which is not.brit tle at'low temperatures, which does not corrode the metallic partsto which it is 'applied and which possesses extremely desirable Ielectrical properties. This medium comprises polymerized aliphaticmono-olefins varying in physical characteristics from viscous liquids totough elastic solids similar to crepe rubber. The leakance anddielectric "constants of these materials are particularly low and'theymaybe'obt'a'ined commercially substantially airee mm any deleterioussubstance winch 'corrodes the conductor. or other 1 apparatus.'F'u'rther, their physical characteristicsar'e such that they areadaptablerto use under a wide range of temperatures;

Chemically, the polymerized aliphatic olefins are among the most'highlystable high polymeric organic materials known. They are pure hydroperchaor para gutta.

carbons and free from any wanna or con ducting substance. They have anextremely low water absorption which is almost negligible and they havean extreme resistance to oxidationand in this latter respect aresuperior to rubber, gutta This oxidation resistance is due primarily tothe saturated nature of the polymerized aliphatic mono-olefin molecules.

The polymerized aliphatic mono-oleilns may be employed alone or as aningredient in mixtures with other materials such as high melting pointwaxes, rubber, gutta percha or balata. The particular type ofpolymerized aliphatic monoolefins employed depends to a great extentupon the use to which the apparatus for which it serves as an insulatingmedium is subjected. When these substances are mixed with othermaterials to produce an insulation composition. the amount employedvaries with the use of the composition. For example, the polymerizedaliphatic mono-oleflns may be employed as a compounding ingredient inrubber mixtures used for coating conductors. In some cases the paramountconsideration is the utilization of the superior electricalcharacteristics of the polymerized aliphatic mono-olefins which comprisea relatively high percentage of the composition,

halide as a catalyst such an anhydrous alumiv num chloride, stannicchloride, boron fluoride, titanium chloride, etc. For the polymerizationthe aliphatic mono-olefin or a mixture of aliphatic oleflns is dissolvedin butane. Subsequent to the polymerizatidn reaction conducted forvarious periods of time at temperatures usually below --10 0., thecatalyst is removed by filtration, washed and the butane distilled fromthe polymerization product. Preferably, the aliphatic mono-olefincontains from 4 to carbon atoms and branch chain mono-oleflns arelikewise preferred over the straight chain variety since the formerpolymerize more quickly and are more readily obtainable commercially inlarge quantitiesthan the latter. Examples of the preferred aliphaticmono-olefins from which the polymerized products of this invention areemployed are the isomers of butylene, amylene, hexylene, heptylene,octylene, nonylene and decylene. Isobutylene due to its relativecheapness and its ease of polymerization is particularly well adaptedfor large scale production of polymerized products. In thepolymerization of the mono-olefins, the mono-olefins intermolecularlyreact to link together with the elimination of most of the double bondand the resulting product is substantially saturated. By the properselection of a particular aliphatic mono-olefin or a mixture ofaliphatic mono-olefins and by the control of the condition ofpolymerization such as temperature, polymerized products are obtainedwhich vary in physical characteristics from viscous liquid to solidelastic materials. Perhaps the best criterion for differentiating thepolymerization products from each other and for serving as an index ofthe physical characteristic of the polymerization product in themolecular weight as determined by the Staudinger viscosity method.Polymerized aliphatic monooleilns having a molecular weight of from10,000 to 150,000 as-determined by this method are preferred forelectrical insulation.

The polymerized mono-olefins may be em polymerized reaction product maybe mixed with rosin or rosin oil or employed alone. I To illustrate theuse of the polymerized mono- I2 of jute is placed over the insulation H.In Fig. 2 a copper electric conductor 20 is covered with an insulation2| comprising polymerized aliphatic mono-oleflns and rubber, balata,gutta percha, high melting point hydrocarbon wax or other materials. Theinsulation It may be vulcanized by the continuous vulcanization processor the older pan method.

The insulation I I of the submarine cable shown in Fig. 1 or theinsulation II of the insulated wire illustrated in Fig. 2 may comprisethe polymerized aliphatic mono-oleilns alone or asan ingredient inmixtures with other insulating materials. Several examples arehereinafter described in which the polymerized aliphatic monoolefins areemployed in compositions for insulating conductors and other electricalapparatus.

EXAMPLES or Comrosrrrorzs Commence GUTTA AND Pommaslzan ALIPHATIGMoNo-OLariNs The following compositions comprising the reaction productresulting from the polymerization of aliphatic mono-oleiins and guttahave been found satisfactory for electrical purposes:

Compo- Compositkm sition. B

Parts by Parts by weight might White leai gutta Polymerized all haticmono-olefin (molecular weight 100,000? 35 Amorphous high melting pointmineral wax (M. I. 160 F.)

' Percent Thick- Loss Spec. cond.

increase Dielectric Spec. res. Compound ness in (3/0 factor constant(mho. (ohm cm) (cm.) weight (i/o0 cmr TREATMENT BEFORE BOA KING Whiteleaf gutta 0. 1485 0. 00 5.4 0. 00043 2. 53 1. 2X10 9. 3X10 ll Whiteleaf gutta 0. 1505 0. 00 6. 3 0.00050 2. 47 1. 4X10 9. 2X10 CompositionA 0.1512 0. 00 2. 7 0. 00022 2. 40 0. 58x10 9. 2X10 Composition B 0.15430.00 2.1 0. 00017 2. 39 0. 45x10 0. 0X10 ll TREATMENT AFTER BOAKINO TWOWEEK White leaf gutta 0. 1476 0. 05 9. 7 0. 00077 2. 54 2. 2X10 9. 6X10White leaf gutta.-. 0. 1512 0. l3 6. 5 0. 00052 2. 52 1. 5X10 9. 3X10Composition A. 0.1522 0.12 5. 7 0. 00045 2. 45 1. 2X10 9. 3X10Composition B 0. 1548 0. 07 5. 2 0. 00041 2. 40 1. 1X10 0. lX l0 llolefins for insulation, reference is made to the accompanying drawing inwhich:

Fig. 1 illustrates a submarine cable insulated with polymerizedaliphatic mono-olefins; and

Fig. 2 shows an insulated conductor in which a rubber mixture comprisingpolymerized aliphatic mono-olefins is employed for the insulatingmaterial.

In Fig. l, a copper conductor I0 is insulated by polymerized aliphaticmono-olefins ll having a molecular weight of 50,000 to 150,000 asdetermined by the Staudinger method. A coating aeeaazsa.

ExAurLEs or Courosmon Courmsnvo Rosana AND PonruaarznnALmnA'rroMoNo-Omrme Compo- Compo- Compo- Composition G sition D sition Esition F Parts by Parts by Parts by Paris by weight weia weight weightPale crepe rubber 30. 30.00 30.00 44. 75 Mineral rubber.. 12.00 15.00Zinc oxide 3. 3. 00 31. 00 Lithoponc 29. 75 40. 00 Whiting 20. 00Polymerized aliphatic mono-cleans (molecular weight 15,000) 2.00 2.003.00 6.00 Retarder (salicylic acid).- 0. 50 0.50 0. 50 S p ur 1.00 1.001.25 1.00 Accelerator (tetramethylthiuram-monosulphide) 0. 25 0. 25 0.25 0. 50 Steer c acid 0. 25 0. 25 0. 25 0. 25 Ceresin wax 0. 26 0. 250.25 Anti-oxidant (phenylalphane hthylamme). 0. 50 0.50 0. 50 1.00Carbon lack 0.50 0.50 1.00 Reclaimed rubber 20.00 Accelerator(diphenylguanidine) 0. 25 Lead oleate 0. 25

The ingredients of the compositions C, D, E or F are compoundedtogether, vulcanized and applied to the conductors by any of the methodswell known in the art. Other fillers, retarders, accelerators, andanti-oxidants may be employed instead or those used in the compositionsC, D, E and F.

The relative amount of polymerized aliphatic mono-olefins in thecompositions C, D, E andF varies from two to six per cent. Thesecompositions illustrate the utilization of the plasticizing propertiesof the polymerized aliphatic olefins in rubber compounds. The resultingrubber insulation has superior dielectric properties tor insulatingconductorsand possesses the necessary physical properties required ofsuch conductors in the field.

As an example or a rubber composition which has a low leakance and lowdielectric constant and in which the polymerized aliphatic monoolefinscomprise the major portion, the following compound has been foundsatisfactory for insulating electric conductors:

Composition G Parts by weight Polymerized aliphatic mono-oleiins-(Molecular weight 100,000) 66. 00 Crepe rubber 34. 00 Zinc oxide 4. 00Stcaric a 2. 00

Anti o x i d a n t (phenylalphanaphthylamine) 1. 50 A c 0 e1 e r a t o r(tetramethylthiuramdisulphide) 0. 20

Sulphur 2 00 Other anti-oxidants and accelerators may be employedinstead of those specified in the above formula. The ingredients aremixed, vulcanized and applied to the conductor in the usual way.

A hard rubber composition having extremely desirable electrical andphysical characteristics may also be prepared from these polymerizedaliphatic mono-oleflns. For example, hard rubber compositions containingthe following constituents may be mixed together and vulcanized for tenhours at approximately C.:

Compo- Composition H sition I Parts by Parts by weight weight Creperubber 70. 00 70. 00 Sulphur 30. 00 30. 00 Polymerlzed aliphaticmono-olefins (molecular weight 60,000) 10.00 20.00

EXAMPLE or COMPOSITION CoMr'nIsINe Wax AND POLYMEEIZED ALIPHATIOMONO-OLEFINS The polymerized aliphatic mono-olefins may also be employedwith hydrocarbon waxes, such oleflns and the resulting compositionsutilized for electrical insulation.

The molecular weight of the polymerized aliphatic mono-olefins specifiedin the compositions in all of the examples are the values obtained bythe well-known Staudinger viscosity method.

While preferred embodiments of the invention have been illustrated anddescribed, various modifications-may be made therein without departingfrom the scope of the appended claim.

What is claimed is:

An insulation for submarine cable comprising 66 parts by weight ofpolymerized aliphatic monooleflns having a molecular weight above50,000, 34 parts by weight of crepe rubber and 2 parts by weight ofsulphur.

. ARCHIE R. KEMP.

